Survey of persons whose professions put them into contact with animals will be made to determine the prevalence of hypersensitivity lung disease, specific antigen sensitivity, and characteristics of the subject immune response. The prevalence of respiratory illness will be estimated by a respiratory questionnaire while the sensitivity to antigens will be assayed by immediate-type skin testing, determination of presence of precipitating antibody, total IgE levels, and specific IgE antibody levels to relevant antigens. Some insight into immune response of the host will be obtained by doing bronchial challenge testing with relevant animal antigens as well as doing essinophile counts and noting the IgE levels. Subjects will have initial simple pulmonary function studies, and complete pulmonary function studies if they are found to have clinical or laboratory evidence of hypersensitivity lung disease. Follow-up screening will be done of all subjects and those with any positive findings will have complete studies repeated yearly for at least two years. Subjects will include the veterinarians of Israel and a selection of animal caretaker personnel in the country. Appropriate controls will be compared for all variables except challenge testing. With this data the question of risk of becoming sensitized to relevant animal antigens should be answered for the test population. Additionally if permanent progressive damage to lung function results from prolonged contact with the source of the anitgens it should be evident from this experience. Suggestions for possible desensitization treatment may result from careful analysis of the sources of antigen sensitization such as urine and serum of the relevant animals as well as the usual skin and hair sources previously studied.